In the last few years there has been a lot of chatter about hydroponics, a method of growing plants without soil. Growers discovered a long time ago that some plants grow better in water than in soil. In fact, plants only need sunlight, water, and nutrients to photosynthesize; nutrients don’t necessarily have to come from soil. Today, many of the vegetables we buy at the store—including vine tomatoes—are grown hydroponically.
Why, then, you might ask, does conventional wisdom dictate that gardeners grow plants in soil? There are pros and cons to each method, as discussed below. First, we provide a brief tutorial on hydroponic growing to enable a better understanding of how it differs from growing plants in soil.
What is Hydroponic Gardening?
Hydroponic gardening entails growing plants in a liquid solution consisting of water and nutrients (fertilizer)—in place of nutrients typically found in rich soil—along with an inert medium to serve as an anchor to support the roots. The growing medium delivers the necessary moisture and oxygen that allow the plants to grow. Note that there is a particular type of hydroponics system, called aeroponics, that doesn’t use a growing medium; it only uses a liquid solution (described below).
For a conventional hydroponics system, there are all kinds of inert growing media that can be used. Popular material include rockwool, grow rock, perlite, coco fiber or chips, vermiculite, pine shavings or bark, gravel, and sand. The key characteristics of a good growing medium is that it won’t decay and break down quickly and won’t absorb so much liquid that it becomes soggy. Roots need to be moist but not soaked; otherwise they’ll rot.
Types of Hydroponics
Hydroponic systems come in two general forms: passive or non-recovery, and active or recovery. In one type of passive or non-recovery system, the nutrient solution is absorbed by one or more wicks or by the growing medium. You can’t cycle or reuse the solution; it’s in the medium.
In active or recovery systems, a pump actively moves the solution. Here, a nutrient solution recirculates, much like water in a fish tank. Active systems tend to be more effective as they will consistently supply adequate oxygen to root systems and your plants will be more likely to reach their fullest potential. Passive systems can become water-logged wet and fail to provide enough oxygen.
The Wick System
In this passive, non-recovery system, the nutrient solution travels, by way of capillary action, from the reservoir to the roots through a wick—candle or lantern wicks work great. This system is inexpensive and simple to set-up and maintain. However, passive systems run the risk of keeping the growing medium too wet and, thus, are not the most efficient manner of hydroponics.
The Ebb And Flow System
This active system uses a submersible pump to move the nutrient solution into a tray positioned above the reservoir which holds the plants. When turned on, the pump fills the tray until liquid levels reach an overflow pipe and drain into the reservoir. Typically, the grower keeps the pump on for about a half-hour (one “flood cycle”). After the flood cycle, solution will drain back down through the pump.
During flooding, stale air is removed from the roots by the rising nutrient solution. When the nutrient solution drains, oxygenated air is pulled into the growing medium. The results are well-oxygenated roots ready to maximize nutrient absorption.
The Ebb and Flow system works best with rockwool or grow rocks as a medium and is a highly effective system, overall, and simple to maintain.
Nutrient Film Technique (NFT)
NFT is an active system using a pump and recirculated solution. Here, the pump pushes solution into a grow-tube in which the roots are suspended. This tube is angled so the solution washes the roots and falls back into the reservoir. This can be done all day, every day.
Roots still need oxygen, so grow-tubes are often filled with capillary matting or air stones (typically used in fish aquariums). The plants are supported by collars or in a grow-basket. No grow medium is used in this system, which is highly effective. However, because the system lacks a growing medium, any significant interruption to the root wash can result in dried-out roots which could be the death of your plants.
Another active system, the continuous drip system, uses a pump and supply lines to each plant. Each line typically uses a drip emitter, which can regulate the amount of solution each plant receives. A drip tray beneath the plants catches the solution and returns it to the reservoir. Continuous Drip systems work best with rockwool, but any medium can be used to good results due to the degree of control gardeners have thanks to the drip emitters.
Advantages of Hydroponics
- Plants grown hydroponically have been shown to mature 30-50 times faster than plants grown in soil—a significant difference
- Along with a faster grow time, hydroponic plants will typically have a greater yield, possibly due to extra oxygen in the various growing media that stimulate root growth. If your roots are getting more oxygen, they’re able to absorb nutrients more quickly. And when mixed with water, root systems are directly fed—there’s no need for the roots to “search out” nutrients from soil. Consequently, the plant doesn’t need to expend as much energy to get the food it needs. In turn, all that excess energy is routed into growing faster, and with better yields.
- A smaller root footprint means more plants per square foot leading to increased yields (an important point if you’re growing in constrained space, like indoors).
- Since hydroponic growing is easiest to do indoors, you’re not susceptible to the vagaries of the weather and can grow plants year round.
- An added and important advantage of hydroponic plants is they have fewer issues with pests, fungi, and disease since they’re grown in a controlled, more hygienic environment.
Disadvantages of Hydroponics
- Potential cost of equipment
- Hydroponically grown plants typically require more care and attention than their conventional, soil-grown brethren.
DIY Hydroponic Systems
While you can buy a hydroponics kit, you can also create your own DIY passive system for a fraction of the cost of buying a kit. There are various online resources to help you get started, depending on the volume of plants you hope to grow. Basically, though, you’ll need the following:
- Watertight growing container(s)
- Some type of growing medium—there are plenty of inexpensive or free options, some of which were listed above
- Hydroponic nutrient mix—you can buy a premixed solution or create your own. The latter requires some research to make sure you deliver the necessary nutrients to your particular plants
- Clean water
- If you’re growing plants indoors, you’ll need adequate sunlight or artificial grow lights
Related to the last point listed above, growing plants successfully indoors—whether via conventional or hydroponic means—is challenging, particularly when it comes to ensuring they get enough light. Unless you have a greenhouse or an indoor garden area in front of large south-facing windows, you will have to invest in grow lights. You also need to manage the ambient air temperature and humidity, especially in winter in northern climes, to make sure it’s not too hot, cold, or dry.
Growing Plants Hydroponically — From Seed
One of the best things about growing plants from seed is that you can choose the EXACT variety you want; you’re not at the mercy of your local nursery’s stock choices. In addition, seeds cost very little, compared to the plant starts you can buy at the store. Combining the benefits of growing plants from seed and growing plants hydroponically is a win-win.
Once again, you will need to do your research to help ensure your success. Seeds are very sensitive and need just the right amount of light, heat, moisture, and oxygen in order to germinate and grow.
Also, choose carefully which plants you want to grow. If you’re planning to grow vegetables, we recommend starting with ones that are easy to grow such as leafy greens like lettuce or spinach or herbs. Once you’ve done that successfully, you can branch out into other green delicacies.
In recent years, as consumers become more interested in where their food comes from, there has been increased interest in hydroponics as a sustainable method of gardening in small spaces. It’s not a new method of growing crops; it’s been around through the millennia. With good reason: it works.